Integrated photovoltaic devices have a basic structure wherein a transparent electrode layer, an amorphous semiconductor layer, and a metal electrode layer are superposed on a transparent insulating substrate. An example of such integrated photovoltaic devices is described below with reference to the amorphous silicon (hereunder abbreviated as "a-Si") solar cell illustrated in FIG. 2. The a-Si solar cell system shown in FIG. 2 comprises a plurality of unit solar cells that are connected in a series or series-parallel fashion and each of which comprises a common transparent insulating substrate that has a transparent electrode layer, an amorphous semiconducting silicon layer, and a metal electrode layer superposed thereon. The metal electrode layer is composed of the combination of back electrodes and lead wire connecting terminals. More specifically, the a-Si solar cell system comprises a single glass substrate 1 that has transparent electrodes 2 (21-23), a-Si film regions 3, and back electrodes 4 (41-43) superposed thereon to form a plurality of unit solar cells. The individual unit solar cells are interconnected via channels 50-52 such that the back electrode of a unit solar cell contacts the transparent electrode of an adjacent unit cell. Lead wires are connected at terminals 40 and 43 in the form of a metal film. Lead wires can be connected either by soldering them onto an adhesive-backed electroconductive tape that is attached to the terminals 40 and 43 or by directly connecting them to the terminals with the aid of an electroconductive adhesive.
These conventional methods of providing lead wires have a common problem in that they reduce the production rate of finished solar cell systems. In the case of using adhesive-backed conductive tape, attaching them to the terminals is a time-consuming operation, and when using a conductive adhesive, an extra step of drying the applied adhesive is necessary.